Extraction process



March l5, 1938. F. c. CUTTING ExTRAcTIoN PnocEss Filed Mayan., 1955 Patented Mor. 15, 1938 eniiett om'oiie'rioit metete moet iD. i'ottimt', im iiio., tittitioor to @heit meveiopmemt 'Commento Som M'etieieto ioiiit, e, eomerotieii oi meiotviti'e .iitiiiiietitiem iiiiiw ti, iiiittt iieriei rie. tiiiii it @iti-toit itt, imite-iti invention reietet to 'eirtteetioii iiroeeteeii miti eoiistitiites ein improvement tiiereoi' tiiieeteii to iritreritethe Metti improve tite purity ei eiiiitteiieet er @teures oi siiitettitieee ivmeii tire oitu it teint-mi iiv extreetiom oi iiotiie'i iriiittiites emittinioe tite stime, emi te permit tire oiieretioii oi .tutti origit'oeee iii eti eeorieimiieoi mettiti'.

iifiiiie eetreeti-oo proeeeeer, ion' .teiitrttioe tiie eomooiieiits oi' iititiiti riiiittiitet 'were itiiovvi'i iii i'or e, ione' time, tite oi texi rettori es reti ieeeiiteti the iiieiti ettari/or pitiitiy mi tite eti@ te ieti orotiuete is ortiiiieiiiy eoiieiriereci te te iiiiiiteti iii? the tiisseivirir; minimi-tir miti eeieetivity oi seive'rit et the moet ievortiieie oioerettiram i5 tempt-erettile. mivooeeiiieiitiri tiiis iii-rt, time iiriiioiiiie et' oouritetemreiit oiierotioizi is iiovv toeim@ tvitieiy retentit' it been prorieseai to ettroet iititiiri iiiiittiii'ee et meent oi tvs/o toit/ente :Howlett mi eoiiotetemvreiotiir te emi in eoiitezet Witi'i each other, eiriri titroiifgii time mixture iieiiit' errtiooteti, tviieteiiy eoriipoiierits soiui'iie im. tite oorreersorifiiiit,V toiverite aire .i from tiie mixture. it

eieo iieeri tirerioeeoi to eiitittitiite @rie oi tutti Eaii selective seiveiitt im one oi? tige tomrooiierite 1ereviotleiy sentite" item tite mixture, e. e., e rior tiem oi tiie e itte'ii.

ifiee oise tieeri otorieseti to operette the eit-1 tteetiori so tire extret emi remette iii etre serieteteiv tetiioveti from time extreetiom torte, oi' eriiorriti omi the eittreet obese etiiiieii. The eiiiiieti @time is ti'iereiiy eeiiiseti to ee tite inte secondary eittreet emi secondary re mete pirates euttitie oi tine eittioetiori zone.

i secondary roiiiriete these is tiren returrieai 'to tire extreetioii zone et rioiiit tiem the erimririg ieeii ei time iitiuiti beine' eittreetefi or et poiot retrieved item it se tte to loess eouritereui'remtiy to primo-w eittroet miese. iii is ori oiiiect oi mv invention to provide o,

iereeess Wiriieh vvii seperate the groups oi suiesttiiiees eoriteimeri im the mixtures being extroeted mote @timely tirati eeetiveiir tintin is poesiiiie `with otoeesses new itriovvn, with the seme cost oi otieretiori emi eiiuiptrieiit, miti which Wiii eHeet time salme degree oi' eeperetiori es the eioremeri tiorieti goiior process with o substei'itiei saving in oiierotine miti/er instelietioo costs.

in the solvent extraction of liquid mixtures to ii@ seperate them into portions which ere relatively more soluble and less soluble in selective solvent, e, iiquiei mixture is mixed or extracted ooontereurrentiy with a, seective solvent in the proportiori and under conditions causing the information 55 of two liquid phases, which can be separated by Aii tiret-tei retto to 'settling et eeiittiiiieiim iteetoee oi time tiiti'ereiice iii, their densities.

Consider, im@ erroiiiiiie, et iitiiiiti mixture oem loivisiriri' oorriiioiierits 'ii 'enti E tviiieii testeo tiveii, ieee seiiiieie miti more eeiiitie ivi eeieetive soiverit i?. this mixture ie eenteoteti vvitii eeieetive soivetit G iiiitier trotter eomriitioiis et teiiioetettire eed eeiieeritretion ttvo eorijtieete pilotes ei diiieveiit eoitiiioeitioris Wiii ite ioizriefi.. @i ti1ese,tiie site iVm-e Wiii eoritoiii im o iii e originel mixture, enti Iattimi:etieieie eiiiotmt :tie eoiiiiiiiitv eti-ii themen terietiet oi time f i mow tire ori imi-"ii o titre teiiei. iii' iii? o emitl tiene iii eourrteretirrerit itfietiiofi it eeeoroee riteeiiiie to otteiri ett eee eiiti oi? eirtreetiem eerie e reife titte wetting' e, eoiiiigiotitiem tviiioii is emite itee imm tty reiiiotitig; t3 it this tiiti :mote pilote, mete eoiieetiiirg eti. ete-:otioiiv l.. oi it Toe oi "iire eoitiriomeiitiii wiii te oreieteiif'- L toiveti in tito etti' which This entire-iet i ewe'ver, geit" 'eiiit een teiii veriotie emoiiiite ei it. To eieet it iiitgii degree oi? iiettveeri i-i omi ist' suivent eittreetioii iiietitcitie, it iieoeeeory tiitit tite retto oi' iii to iii ettrtiet these ite es io'tv possiioien in, mttietiotie iii tviiieii it emi ete eotoioifx-iteit7 mic iiiie ie temperature employed,

er met' riet tente ei iii tieriemtiiorg there existe e rieiiriite minimum tot this tetti@ eiztreet @time eoiiteiriirig miesteiitioiiy tio ii. it 35i' is @restreinte to produite ettieet otieisee in which tite retio oi it to 'it ie es eioee pre-etieei to these minime.

Tite velue oi ti'iie retto which @titties iii. pet tieiiier sitiietiori detentie miem the eorriiiositiori oi' the originel teeti, upon tite qlieritity/ oi soivent useti, upon time tempeottire enti troon tine eoivent choroeterieties of tite eemooiiemte :it E emi il et" tine temtierottite meti ood will met, iii generaal, correspond to these tiesireci minime. i iittve 4&5 ioiiiiti tiiet in tite eittreotiem ot mi iii-H mixture, vvitii eiireiereritiei eoiveiit ior B, to produite euhsteotioiiy pur-e ii, time oiiemtitv oi soir/ent empioveoi generaiiiy eiteeetie that which ie necessary to produce ein extract phase of the `invest eoimpo- 50 sitiom, i. e., 'which wiii produce ein extract phase iler/ine time iowest ii te E motie obtainable for the temperature employed.

The present invention provides .e method oi' extretioxi or obtaining an improved extract, i. e.,

one whichcontainsA andBin a lower ratiothan is otherwise obtainable, without resorting to more selective solvents or to low temperatures. Hy invention consists in withdrawing from'an extraction sone the extract phase produced by any ydesired 'extraction process, hereinafter referred to astheprimaryextractphase,andremoving from saidprimaryextractphsseaporionofthesolvent containedtherein-by any suitable means, as by absorption. precipitation, or 4 distillation. bringing the resulting solvent-poor extract phase, by cooling. if desired, to a temperature at which it will separate into secondary extract and secondary rai'nnate phases, and separating these phases; the remainder of the solvent may then be removed from either or both secondary phases.

. This treatment of the primary and subsequent extract phasesmay be repeated, if desired, al-

though by proper temperature regulation a highly concentrated extract may be produced in a single step. Only so much solvent is preferably removed as to produce an extractphase having the minimum A to B ratio attainable with the particular solvent at the temperature selected for the separation into secondary railinate and extract phases. Hy process is not limited to any particular temperature for this second separation, although it is preferable to maintain this temperature at the same value as that prevailing at the point of the extraction none at which the primary extract phase is formed, or below this value. It is. however, also possible to use higher temperatures.

Thesecondary raiilnate may be withdrawn as a separate productly It is, however, often advantageous to return it to the extraction zone to contact or wash the primary extract phase. This washing may be elected in any manner, although I prefer toiiow the secondary radlnate countercurrently to the extract phase; it` causes a considerable amount of the less soluble components to be dissolved in the secondary ramnate phase,

thereby improving the composition of the primary extract phase. In operations in which the secondary' rafilnate phase is used in this manner It may be desirable to determine the quantity of solvent removed by the consideration that thesecondsry raillnate phase is produced in the de-` sired quantity to `permit effective washing of the primary extract phase in the main extraction or washing sone.

In order to more fully describe my process, reference is had to the now diagram illustrating a preferred embodiment of my invention.

- According to a continuous method of operation, as illustrated by the drawing, a liquid mixture to be extracted is led into an extraction apparatus I through an inlet I. This apparatus may consist of a packed tower, or a number of countercurrent washing stages, or of any other type of apparatus which is suitable for countercurrent washing of one liquid phase with another. A suitable solvent, or a solvent mixture, is introduced into the apparatus I by a pipe I. Primary raihnate and extract phases are removed respectively through outlets l and l. In practice, the length of the extraction sone, or the number of mixing -and settling stages, that is, the zone, or sones, where the feed is extracted with the solvent, is so selected as to insure the desired composition of the nnal raiilnate phase. The extract phase outlet l may be substantially away from the feed inlet I, as shown, so as to provide a sone for washing the extract phase formed near the feed inlet 2. It is often advantageous in provide the extraction apparatus with temperature regulating animo wherebyrthe washing aoneor the entire extraction apparatus maybe operated at a temperature gradient. librexample, I have obtained excellent results by maintaining a temperature 100 C.

vention is not limited to'any particular method of producing the primary extract phase, but may be used to improve any extract phase.

The primary extract phase is introduced by a conduit I into the primary solvent separator l,

solvent separator 1 may be of any desired type; such as a distllling column.

The liberated solvent is removed through a conduit I and may be reused. The solvent-poor extract ls withdrawn from the separator 1 through a pipe I and conducted through a heat exchanger Il into separating apparatus II, which may b e either a settling tank or a centrifugal separator, or any' other apparatus which is capable of separating two liquid phases. The heat exchanger I0 is oplted at a temperature which will cause the liquid in the apparatus II to have the desired temperature for the separation of secondary rafiinate and extract phases. This temperature may be slightly higher than that which obtains in the apparatus I, although it should preferably be the same as or lower than that which obtains at the outlet 5.

, vIn the apparatus II the extract and ramnate Alayers are allowed t separate, the latter being discharged through a pipe I2. This ramnate may be used as a source oi' a second grade refined product, or subjected to an additional extraction with a solvent, or it may be returned to the extraction apparatus I, for example, through an inlet I3 near the outlet l.

When the secondary ramnate phase is returned to the apparatus I it may be used as ajackwash for the downcoming extract phases. For effective washing, this backwash must be of such compodtion and in such quantity as to form, upon combining with the primary extract phase, two liquid phases. It may be desirable to ilow the secondary raillnate phase through a heating or cooling device, so as to cause its temperature to be suitably adjusted, for example, to be substantially the same as that which obtains in the f column at its point of introduction.

The secondary extract phase from the settling chamber .II is led by the conduit I9 into the nnal solvent separator Il, where it is substantially freed of the solvent. The solvent separator I4 may be of any desired type, such as a distilling column. The liberated solvent is returned tothe apparatus I through a pipe Il, and the solventfree secondary extract is discharged through a pipe I.. A portion ofthis extract may be recycled through a pipe I1 and mixed with the solvent-poor extract phase before it enters the separator- I I, either before or after the heat exchanger Il, or it may be returned by conduits Il and 2i to the washing sone of the apparatus I instead of the secondary railinate phase introduced in Il.

where it is freed of a portion of the solvent. The v Numerous modifications may be made in my process without departing from the spirit and scope of the invention. l'ior example, the process may be applied to batch operations. In this event other component. -In the present specincation and claims, there is no diilerence in meaning between the words solution, liquid mixture and liquid solution. i I claim as my invention:

1. The process of separating a liquid mixture oi components into two portions which comprises extracting said mixture' with a liquid selective solvent to produce primary ramnate and extract phases, separating said primary phases, removing,

a portion of the solventv from the primary extract phase to produce a solvent-poor extract phase and cause' its separation into two secondary phases, separating said secondary phases, removing the solvent' from the secondary extract phase to produce a nnal extract and mixing at least a portion of said nnal extract with another quantity of solvent-poor extract phase prior to its separation into secondary raffinate and extract phases. A

2. The process of separating a liquid mixture of components into two components which comprises extracting said mixture with a liquid selective solvent in an extraction zoneto produce primary ramnate and extract phases, separating said primary phases, removing a portion oi the solvent-from the primary extract phase to produce a solvent-poor extract phase, adjusting the temperature of said solvent-poor extract phase, to produce secondary ramnate and extract phases, separating the said secondary phases, removing the remaining solvent from the secondary extract phase to produce a final extract and returning a portion oi the i'inal extract tothe solvent-poor extract phase prior to its separation into secondary raiiinate and extract phasesythe amount of solvent present in the solvent-poor extract phase and the amount of ilnal extract mixed with it being such that the composition of the secondary extract is substantially the most favorable which can be obtained at the adjusted temperature. p

3. The process according to claim 2 in which the adjusted temperature is the same as that at which the primary lextract phase is produced.

4. The process according to claim 2 in which the adjusted temperature is substantially below that at which the primary extract phase is produced.

5. The process Iaccording to claim 2 in which the secondary ramnate phase is returned to the extraction zone'.

8. The process oi separating a liquid mixture into two components which comprises extracting said mixture with a liquid selective solvent to produce primary ramnate and extract phases. separating the primary phases, removing a portion oi.' the solvent from the primary extract phase to produce a solvent-poor extract phase and cause -its separation into two secondaryphases, separating said secondary phases, and bringing a portion of the secondary raiilnate phase into contact with the primary extract phase.

7. '111e process of separating a liquid mixture into two components which comprises extracting said mixture with a liquid selective solvent to produce primary ratiinate and extract phases, separating the primary phases, removing' a portion of the solvent from the primary extract phase to produce a solvent-poor extract phase and cause its separation into two secondary phases, separating vsaid secondary phases, and ilowing a portion of the secondary ramnate phase countercurrently to and in contact with the primary extract phase.

8. The process of separating a liquid mixture solvent to produce primary ramna'te and extractA phases. separating the primary phases, removing a portion oi' the solvent from the primary extract phase to produce a solvent-poor extract phase and cause its separation into two secondary phases, separating said secondary phases, removing the solvent from the secondary extract phase to produce the ilnal extract, returning a portion oi the nal extract to the solvent-poor phase, and bringing a portion oi the secondary ramnate phase into contact with the primary extract phase.

9. 'Ihe process of separating a liquid mixture into two components which comprises extracting said mixture with a liquid selective solvent to produce primary raiiinate and extract phases, separating said primary phases, removing a portion of the solvent from the primary extract 'phase to produce a solvent-poor extract phase,

adjusting the temperature of said solvent-poor extract phase to produce secondary railinate and extract phases, separating said secondary phases, and bringing at least a portion oi the secondary raillnate phase into contact with the primary extract phase.

10. The process of separating a liquid mixture into two components which comprises extracting said mixture with a. liquid selective solvent to produce primary raillnate 4and extract phases, separating said primary phases, removing a portion oi the solvent from the primary extract phase to produce a solvent-poor extract phase,

adjusting the temperature of said solvent-poor extract phase to produce secondary ramnate and extract phases, the amount of solvent removed being such that the secondary extractv phase produced has substantially the most favorable composition obtainable at the adjusted temperature, separating said secondary phases, and bringing at least a portion of the secondary raflinate phase into contact with the primary extract phase.

11. The process of separating a liquid mixture into two components which comprises extracting said mixture with a liquid selective solvent to produce primary rai'ilnate and extract phases, separating said primary phases, removing a portion of the solvent from the primary extract phase to produce a solvent-poor extract phase, adjusting the temperature of said solventpoor extract 'phase to produce secondary raiilnate and extract phases, separating said secondary phases, and bringing at least a portion of the secondary ramnate phase into countercurrent contact with the primary extract phase in a plurality of countercurrent washing stages.

l2. The process oi' separating a liquid mixture into two components which comprises extracting said mixture with a liquid selective solvent to produce primary raillnate and extract phases, separating said primary railginate and extract phases, removing solvent from the primary extract phase in such amounts as to yield, upon cooling the resulting solvent-poor extract phase to its original temperature, a secondary ramnate phase in suitable quantity for countercurrently washing the primary extract phase, separating the resulting solvent-poor extract phase into secondary extract and raiilnatev phase at its original temperature, and bringing at least a portion of the secondary ratilnate phase into countercurrent contact with the primary extract 13. The' process oi.' separating a -liquid mixture into two components which comprises cxtracting said mixture with` a liquid selective solvent to produce primary ramnate and extract phases. separating said primary phases, removing a portion of the solvent from the primary extract phase to produce a solvent-poor extract phase, adjusting the temperature of said solventpoor extract phase to produce secondary ramnate and extract phases, separating the said secondary phases, removing the solvent from the secondary extract phase to produce a tina] extract. and mixins final extract with another quantity of solvent-poor extract phase prior to its separation into secondary railinate and extract phases.

f FRANK C. CUTTING. 

